Emergency vehicle (EV) operators needing to move expeditiously through congested urban traffic may nevertheless be unable to do so. Drivers of other vehicles, unaware of an EV""s approach because of limited visibility, air conditioning, sound insulation and/or loud music systems, delay or halt the EV""s progress by blocking its path. Historically, horns, sirens and/or lights have been used to signal an EV""s approach, but such warnings are increasingly inadequate and dangerous. See, for example, the background discussions in U.S. Pat. Nos. 5,235, 329 and 5,495,243, both incorporated herein by reference.
The invention of the ""243 patent relates to improving the efficacy of warning lights on emergency vehicles but requires a line-of-sight to any vehicle intended to receive the warning. The line-of-sight requirement means that warnings can be selectively applied, but the effective warning range is relatively short, particularly in urban environments. On the other hand, while the warning system described in the ""329 patent does not require line-of-sight to a warned vehicle, it is relatively non-selective.
The augmented warnings described in the ""329 patent are intended to assist the relatively few drivers who actually need warnings to react reasonably (as by stopping or turning away from the EV""s path). But many other drivers would, in general, also receive the warnings. These other drivers, who are not in or near the EV""s path, would ideally not react to these false warnings (as by moving to the right lane and stopping) because in doing so they would be likely to needlessly aggravate traffic congestion. In part because it compounds the problem of false warnings, the invention of the ""329 patent tends to increase traffic congestion rather than reducing it. This drawback substantially limits the net benefits of the warnings provided by the ""329 invention.
To significantly improve on the ""329 invention, warning methods and apparatus would preferably be more precisely focused on the vehicles and drivers actually in or near an EV""s path. Since this path is generally unpredictable, warning systems should provide critical information in (nearly) real time to selected vehicles in the vicinity of the EV. Relatively long range predictions of appropriate avoidance maneuvers would confer little benefit, since even the EV driver may be uncertain about an EV""s exact intended path and speed. There may be, for example, a choice of EV destinations (e.g., one of several hospitals for emergency medical treatment), a choice of routes (e.g., alternatives to avoid congestion or road construction), or a moving objective (e.g., a suspect fleeing a police stop or an accident scene). In summary, EV avoidance maneuvers preferably rely on information concerning likely encounters with relatively nearby EV""s, and that information may change abruptly.
Several systems have been proposed to address one or more of the above needs. For example, U.S. Pat. No. 6,160,493 (incorporated herein by reference) describes a radio warning system that reliably transmits warning information, possibly including global positioning system (GPS) coordinates of the transmitter""s location, to any system receiver within the range of a spread-spectrum signal. Extrapolating from successive sets of these transmitter coordinates might reveal an EV""s intended path relative to other drivers.
The use of GPS coordinates to specify a transmitter""s location could improve the value of a warning and reduce the incidence of false warnings, but the coordinates would only be available to the minority of drivers having the equipment to interpret GPS signals. The relatively high cost of needed GPS-related equipment in both transmitting and receiving vehicles would thus tend to discourage widespread adoption of the system. And without widespread adoption, any such system would be only marginally useful. Unfortunately, this situation would not be significantly improved by eliminating the GPS features of the system (i.e., the coordinates). Most drivers receiving a warning signal without at least some information on the transmitter location would experience the false warning problems described above.
Another recently-proposed system described in U.S. Pat. No. 6,326,903 (incorporated herein by reference) includes provision for electromagnetic transmission of information on direction-of-travel from one EV to another EV and/or from an EV to (controllable) traffic signals in its path. Again, the preferred source of direction-of-travel information is a GPS, although other, less accurate systems using a common direction reference (such as a compass) are also described.
A major drawback of all similar systems is that use of a common direction reference, whether based on GPS or another external coordinate system, requires each vehicle in the system to have equipment to access the common external reference. This equipment might reduce the incidence of accidents between EV""s, but its unnecessary cost and complexity would also discourage widespread adoption of the system. And drivers not having access to the common direction reference, being unable to use the system, would be likely to cause about the same degree of congestion and delay as they do now.
Another communication system providing information useful in controlling traffic congestion is described in U.S. Pat. No. 5,448,599 (incorporated herein by reference). The system of the ""599 patent provides reliable spread-spectrum communication between two vehicles, with the option of including speed and distance information for one vehicle relative to another vehicle. Relative speed (proportional to Doppler shift derived from the spread-spectrum signal) could be combined with distance information to inform a driver of his distance from an EV and the speed of the EV""s approach, but not the direction of approach.
The system of the ""599 patent provides valuable information to a driver receiving a warning signal, but the patent describes use of either a retransmitter-receiver pair or a passive reflector-receiver pair to obtain the distance separating two vehicles. Once again, cost and complexity are increased to obtain desired warning information. Further, if passive reflectors were used instead of retransmitters, the reflected signals would be useful only for relatively short distances (about 200 meters in the example provided in the patent).
Thus, as shown by the examples above, the warning systems proposed to date are relatively complex, costly, intrusive and/or ineffective. Lower cost versions of these systems suffer some of the same disadvantages as the old sirens, lights and horns, providing late, false, distracting and/or misleading warnings to too many drivers, while offering insufficient benefits in reducing EV delays and avoiding accidents.
A better warning system is needed to provide timely alerts to drivers who are either within or approaching the likely path of an EV. Such a system should provide relatively selective warnings in nearly real-time, and it should be reliable, secure, relatively inexpensive, flexible and user-friendly enough to be widely adopted. It should also make effective use of each driver""s judgment and knowledge of local traffic patterns, providing supplemental information in a plurality of compatible formats usable by drivers to avoid an EV""s path.
The present invention comprises improved vehicle warning systems that combine certain beneficial features of earlier warning systems with novel elements that confer important advantages in cost, effectiveness and/or operational flexibility. The invention relates in part to encoder-transmitter subsystems for transmitting encoded warning signals and corresponding receiver-decoder-alert subsystems. Each encoded warning signal comprises an ID code which is a unique identifier (e.g., the vehicle identification number) for the vehicle carrying its corresponding encoder-transmitter subsystem. Encoder-transmitter subsystems are typically found in EV""s but more generally found in transmitting vehicles of any type authorized by the law of the jurisdiction in which they operate. To simplify portions of the illustrative discussion herein, transmitting vehicles are referred to as EV""s.
Encoded warning signals of the present invention are locally broadcast from EVs to receiving vehicles, using omnidirectional and/or electronically steerable directional transmitting antennas. These warning signals are received via omnidirectional and/or electronically steerable directional antennas on receiving vehicles. While the invention encompasses any mode of electromagnetic wave transmission employing one or more frequencies, preferred embodiments comprise spread-spectrum and/or ultra-wideband (UWB) transmitters and receivers. The following U.S. Patents relate to spread-spectrum and/or UWB technology and are incorporated herein by reference: U.S. Pat. Nos. 6,351,652; 6,351,246; 6,331,997; 6,327,257; 6,301,311; 6,240,099; 5,363,108; 5,022,046; and 4,761,796.
Receiving vehicles have receiver-decoder-alert subsystems that are preferably considered as much a part of a vehicle""s safety equipment as air bags. The encoder-transmitters and receiver-decoders of respective transmitting and receiving subsystems are preferably comparable in many respects to analogous elements of modern wireless telecommunication systems such as those comprising digital cell phones and those used for local area computer networks. For example, they generally transmit at power levels of 10 watts (in many applications, power levels less than 1 watt) and their multiple-access capabilities (using, e.g., code division multiple access or CDMA) mean that warnings transmitted asynchronously from a plurality of EV""s can be processed in virtually real time by systems in each receiving vehicle.
Further, transmitting and receiving subsystems in a standby mode, like modern energy-efficient cell phones, draw very little electrical power from a vehicle power supply. Because of the relatively large amounts of energy stored in vehicle batteries, such transmitting and receiving subsystems can remain in standby mode almost indefinitely, being virtually always ready for use without any requirement for action by a driver.
Thus, modern communications technologies, including the relatively low cost spread-spectrum and/or UWB transmitters and receivers commonly used in digital wireless telephones and computer networks, offer clear advantages over sirens, lights and horns in reliably reaching drivers within sound-insulated vehicles. And, due to the widespread adoption of digital telephone networks employing asynchronous packet transmission of encoded digital information, such telephone equipment is readily available and can, with little or no modification, be used for encoding, transmission, reception and decoding of warning information of the present invention in packet form.
The presentation of warning information in receiving vehicles is via alert modalities that are intentionally intrusive. Alert modalities are intended to draw the attention of a receiver vehicle driver to the emergency information, notwithstanding distractions that may be present in the vehicle. To minimize the cognitive burden on the driver, delay timer means (e.g., time-delay relays, time switches or delay lines) are also provided to temporarily disable or otherwise modify at least one warning means.
Delay timer means thus function in a manner roughly analogous to the action of a snooze-alarm, which awakens a sleeper with an alarm and then allows an optional (relatively quiet) wakeup period before subsequent activation of a more intrusive alarm. One or more of the (delayed) snooze alarms intermittently remind an awakening sleeper of the need to get out of bed, whereas one or more delayed alerts are provided in the present invention to intermittently remind a driver of important warning information related to vehicular operation.
The provision for intermittent (i.e., not continuous). driver alerts via at least a first alert modality is an additional feature of the present invention. The time periods between such intermittent alerts via at least a first alert modality are established by a delay timer that is triggered by activation of a driver alert sensor. Activation of a driver alert sensor indicates a driver""s acknowledgment of a warning.
Delay of a subsequent alert after a driver alert sensor activation may be either adjustable or of predetermined duration, and is both reasonable and beneficial in augmenting safe vehicle operation. Without sacrificing a driver""s situational awareness of a warning, such an alert delay reduces the time-average cognitive burden tending to distract a driver from the primary task of vehicle control. U.S. Patents having useful background information include U.S. Pat. Nos. 6,281,806 and 6,181,996, both incorporated herein by reference.
Since the warning information underlying activation of an alert modality may change quickly, the delay period after such a driver alert is acknowledged is preferably terminable on receipt of new warning information. The new information might comprise, e.g., a change in velocity of an approaching EV or reception of a warning signal bearing a different ID code.
It is also preferable to ensure that any delay period is initiated only within a predetermined time period following a driver""s activation of the driver alert sensor. The possibility of a driver activating the alert sensor too early (i.e., erroneous acknowledgement in the absence of an alert), or too late (i.e., lack of acknowledgement or late acknowledgement after an alert has actually been presented to the driver) is preferably detected by a response timer. When present, the response timer measures the time period between activation of at least one alert modality by an alert system interrupter/controller and activation of the driver alert sensor.
A response timer may also furnish information useful in modifying the duration of an alert delay and/or adjusting the performance characteristics of one or more alert modalities (e.g., alarms and/or displays) to better suit an individual driver. For example, late or absent activation of a driver alert sensor following an alert may be followed by an increase in the loudness and/or changes in other characteristics of an aural warning modality. Analogously, the intensity (and/or color, distribution, repetition rate or duty cycle) of light from a visual display may in certain embodiments be made adaptive to the response timer and/or to other parameters such as an EV""s movement with respect to a receiving vehicle. U.S. Patents related to alarms and displays include the earlier cited ""329 patent as well as U.S. Pat. Nos. 5,963,148, 5,920,194 and 5,889,475, all incorporated herein by reference.
Movement of an EV toward or away from a receiving vehicle (reflected, for example, in the estimated closing velocity between the two vehicles) is readily estimated by using time codes embedded in the signal received from the EV or by detecting Doppler shift in that signal. When an EV is not closing with a receiving vehicle, i.e., when the EV is traveling parallel to or away from a receiving vehicle, at least a first alert modality (preferably aural) is preferably attenuated or eliminated. Simultaneously, at least one additional alert modality (preferably visual) is preferably modified to indicate that the EV is not closing with the receiving vehicle.
When a plurality of EV""s simultaneously transmit warning signals to a single receiver-decoder-alert subsystem having either an omnidirectional or directional antenna, each signal is decoded, and represented to the driver, individually. This is accomplished in part in the present invention because each of the transmitted warning signals, though they arrive at the receiving antenna substantially simultaneously, can be distinguished (e.g., through one or more unique carrier frequencies or a unique CDMA multiple access code).
Additionally, since each warning signal carries a unique EV ID code (analogous, for example, to a telephone number or information contained in a subscriber identity module), all warning information associated with a particular signal can be identified to a driver as relating to a single EV. Warning information that may include, for example, the corresponding EV""s speed, its orientation relative to the receiving vehicle, or the received signal strength, is associated in the receiver-decoder-alert subsystem with the respective EV""s ID code. This process of association is analogous to well-known methods in the telecommunications industry for preparing electronic records that associate billing information with particular telephone numbers. Examples of such methods are described in U.S. Pat. No. 6,332,579, incorporated herein by reference.
The above association of warning information with a particular vehicle ID code may also include the estimated azimuths of directional transmitting and receiving antennas on the transmitting and receiving vehicles respectively. These azimuths can preferably be estimated through use of electronically steerable directional antennas connected to the encoder-transmitter and receiver-decoder. Each such antenna can be steered so as to scan all azimuths or a subset of azimuths under the control of an antenna director.
Directional antennas are well-known in the art and commonly comprise a rotating horn or loop, or an array of elements. Representative methods and apparatus related to directional antennas are described in U.S. Pat. Nos. 6,323,802; 6,313,795; and 6,313,794, all incorporated herein by reference. A preferred form of directional antenna that is relatively inexpensive, rugged, and electronically steerable is described in U.S. Pat. No. 6,288, 682 (Thiel et al.), incorporated herein by reference.
The antenna director for each directional antenna of the present invention acts through its respective encoder-transmitter or receiver-detector to steer the antenna. For an antenna in receiving mode, a preferred steering criterion is maximization of the received strength of each individually-identified warning signal, producing in turn an azimuth signal corresponding to the azimuth at which each individual signal strength maximum occurs. For an antenna in transmitting mode, preferred steering criteria may include, for example, substantially uniform coverage in a horizontal plane or, alternatively, a transmission pattern that includes all vehicles within signal range with which the transmitting vehicle is closing.
Each estimated azimuth corresponding to a received signal as described above is associated with the ID code of the vehicle transmitting the signal in question. In a receiving vehicle, the estimated closing velocity and azimuth signal are directed by the alert system interrupter/controller to appropriate alert modalities for presentation to a vehicle driver. Each transmitting vehicle represented in such a plurality of alert modalities may then be represented individually by, for example, a corresponding plurality of characteristic sounds, colored lights, and/or icons on a graphical display.
As described above, the means for alerting a receiving vehicle driver to whatever encoded warning may be contained in a received signal comprises at least two alert modalities corresponding to two or more of the driver""s senses (e.g., sight, touch, or sound). An alert system interrupter/controller activates the alert modalities and also offers flexibility in representing warning information in alternative ways. For example, one or more characteristics of an aural alert (such as tone, pitch and/or volume) may increase with higher closing velocities. Various EV types such as fire trucks, police cars, and ambulances may be represented to a driver through distinctive icons and/or color coding on a visual display, and/or through characteristic-sounding audio alerts. Audio warnings are preferably delivered by interrupting (i.e., preempting any non-emergency use of) a vehicle""s built-in sound system.
Interrupting the speakers in a vehicle sound system to alert a driver to easily-recognized warning sounds is among the most cost-effective alert modalities and would frequently be preferred if only a single alert modality were to be presented to a driver. Through interruption of a vehicle sound system, highly specific aural warnings can be conveyed. These include, for example, synthesized speech or a sound that increases in pitch, tone and/or loudness as an EV approaches. But such aural warnings can be degraded by, for example, a driver""s deafness, ambient noises (as from open windows), and/or multiple simultaneous warnings from different EV""s. Thus, a plurality of alert modalities, including at least one non-aural modality, is preferably presented to each driver. Different drivers may prefer to customize the types of alert modalities and/or the manner of their presentation, and the alert system interrupter/controller may facilitate such modifications.
In certain preferred embodiments, a portion of the functions of a receiver-decoder-alert subsystem are preferably handled by a programmable processor. Such a processor can digitally simulate one or more of the functions of the elements described above, such as a response timer, a delay timer, an antenna director or a Doppler shift detector. Such a programmable processor is preferably located in the alert system interrupter/controller and may thus conveniently provide specific synthesized voice warnings as an alert modality in conjunction with vehicle speakers.